Examples of mechanical circulatory support systems (MCS) include ventricular assist devices (VADs). A VAD is a mechanical pumping device capable of supporting heart function and blood flow. Specifically, a VAD helps one or both ventricles of the heart to pump blood through the circulatory system. Left ventricular assist devices (LVAD), right ventricular assist devices (RVAD) and biventricular assist devices (BiVAD) are currently available. Also, circulatory support systems may include cardiopulmonary support (CPS, ECMO), which provide means for blood oxygenation as well as blood pumping. Such devices may be required during, before and/or after heart surgery or to treat severe heart conditions such as heart failure, cardiopulmonary arrest (CPA), ventricular arrhythmia or cardiogenic shock.
Traditionally, VADs are fitted during open-heart surgery through an incision in the chest and the procedure involves puncturing the apex of the left ventricle to re-route blood from the ventricle to the aorta through an external pump. An example of a device used in a surgical VAD is HeartMate II™. Such surgical procedures are clearly invasive and unsuitable for weaker and vulnerable patients as they involve a greater recovery time and carry the risks of infection and trauma. This is particularly the case in the treatment of children for whom existing surgical equipment and devices are comparatively bulkier and more invasive, and a reduction of the size of the equipment is often difficult if not impossible in view of the equipment and procedure involved. Furthermore, these devices require the intervention from a team of skilled surgical staff in a hospital environment and are therefore less available and costly.
More recent procedures are non-surgical and involve the insertion of a VAD through a small incision made at the groin of the patient. A popular version of such so-called percutaneous VAD is the TandemHeart™ device. A tube is introduced through an incision adjacent the groin of the patient and advanced along the femoral vein and inferior vena cava, across the intra-atrial septum and into the left atrium so that oxygenated blood from the left atrium is fed into a pumping device located outside the patient's body and recirculated through an outflow tube into the femoral artery. Although this device has shown promising results, it only provides short-term support (up to two weeks) and is unsuitable for long-term treatments. The external pump is bulky and requires the patient's immobilization for as long as the device is fitted. Furthermore, there is a risk of life-threatening infection around the groin incision, which remains open during the treatment, and of considerable bleeding from a major artery. In addition, the tube of the TandemHeart™ ends in the left atrium from which blood is pumped out and led outside the patient's body. This type of blood inlet system can potentially become hindered, if not blocked, if surrounding tissues are accidentally sucked in, thereby resulting in a loss of efficiency.
Another popular percutaneous VAD is the Impella™ device, which is inserted into the femoral artery and descending aorta. The Impella™ device comprises an elongated end, which is implanted across the natural aortic valve, with a blood inlet placed in the left ventricle and a blood outlet above the aortic valve. A pump circulates blood from the inlet to the outlet. The driveline is externalised through the femoral artery during use and the same limitations apply as with TandemHeart™ and other current percutaneous MCS systems. This device is approved to provide support for up to a week. There is therefore a need for a device with reduced risk of infection and bleeding and increased mechanical stability which can be used as part of a short-term “bridge to recovery” treatment or as a long-term treatment including patient mobilisation. In addition, the efficiency of the pump is limited because it is not possible to insert a pump of the size required to provide a suitable blood flow using percutaneous arterial access. Presently, the problem of limited pump capacity and duration with percutaneous MCS is solved either by inserting larger intracorporeal pumps surgically or by choosing an extracorporeal pump, with all the potential problems as described above.
Known mechanical circulatory support systems are positioned within the patient directly though open-heart surgery or indirectly for example using transcatheter methods in which the device is pushed to its intended position. Such a transcatheter method is described by the Applicant in PCT/EP2015/055578, expressly incorporated herein by reference. These methods involve the implantation of a guide wire extending for example from the patient's groin area, along the femoral vein, up the inferior vena cava into the right atrium, through the atrial wall into the left atrium, through the atrial roof and aortic wall into the aorta, so that the proximal end of the guide wire is outside the groin area of patient and the distal end is in the aorta. The guide wire assists in the subsequent positioning of catheters and/or sheaths through which the various devices are pushed to their target positions.
It has however been observed that the ability to accurately guide and position the devices is affected by factors such as the target position, for example, where the device is to be moved through or positioned across anatomical walls, and/or at awkward angles. There may also be some issues with the coupling between the guide wire and the device to be delivered. Ideally, the guide wire is positioned slidably and centrally within the device. Depending on the structure of the device, this central positioning is not always achievable and the device is pushed alongside the guide wire in the catheter. This potentially can result in a less accurate, and therefore less safe, device delivery process.